Spiny calretinin-immunoreactive neurons in the hilus and CA3 region of the rat hippocampus: local axon circuits, synaptic connections, and glutamic acid decarboxylase 65/67 mRNA expression

We have used the Golgi method and Golgi electron microscopic techniques to analyze the axonal arborization and efferent connections of spiny calretinin-immunoreactive neurons in the CA3 region and hilus of the rat hippocampal formation. In the hilus, the axons of spiny calretinin-immunoreactive neurons sent out numerous collaterals that arborized in the hilar region and the molecular layer. In the CA3 region, these axons extended mainly to the stratum radiatum and pyramidal layer but also to the stratum oriens and stratum lacunosum-moleculare. Axonal varicosities were distributed widely throughout the axonal collaterals. Electron microscopic studies revealed that the axon terminals of spiny calretinin-immunoreactive neurons established synaptic contacts mainly with dendritic shafts. We next analyzed the expression of glutamic acid decarboxylase (GAD65/67) mRNAs in spiny nonpyramidal neurons that were identified by calretinin immunoreactivity. We found that spiny calretinin-positive neurons in the CA3 region and hilus of the rat hippocampal formation expressed the two isoforms of GAD: GAD65 and GAD67 mRNAs. These findings show that the spiny calretinin-immunoreactive neurons of hippocampus give rise to local axonal arborizations, suggesting that they are inhibitory.

Reelin regulates the development and synaptogenesis of the layer-specific entorhino-hippocampal connections

Here we examine the role of Reelin, an extracellular protein involved in neuronal migration, in the formation of hippocampal connections. Both at prenatal and postnatal stages, the general laminar and topographic distribution of entorhinal projections is preserved in the hippocampus of reeler mutant mice, in the absence of Reelin. However, developing and adult entorhinal afferents show severe alterations, including increased numbers of misrouted fibers and the formation of abnormal patches of termination from the medial and lateral entorhinal cortices. At perinatal stages, single entorhinal axons in reeler mice are grouped into thick bundles, and they have decreased axonal branching and decreased extension of axon collaterals. We also show that the number of entorhino-hippocampal synapses is lower in reeler mice than in control animals during development. Studies performed in mixed entorhino-hippocampal co-cultures combining slices from reeler and wild-type mice indicate that these abnormalities are caused by the lack of Reelin in the target hippocampus. These findings imply that Reelin fulfills a modulatory role during the formation of layer-specific and topographic connections in the hippocampus. They also suggest that Reelin promotes maturation of single fibers and synaptogenesis by entorhinal afferents.

Proliferation, migration and differentiation of neuronal progenitor cells in the adult mouse subventricular zone surgically separated from its olfactory bulb

The subventricular zone of the adult mammalian forebrain contains progenitor cells that, by migrating along a restricted pathway called the 'rostral migratory stream' (RMS), add new neurons to the olfactory bulb throughout life. To determine the influence of the olfactory bulb on the development of these progenitor cells, we performed lesions that interrupt this pathway and separate the olfactory bulb from the rest of the forebrain. By labelling cells born at several survival times after the lesions with the thymidine analogue bromodeoxyuridine (BrdU), we found that disconnection from the bulb influences the rate of BrdU incorporation by the progenitor cells. The number of labelled cells in lesioned mice was almost half that found in control mice. In the disconnected migratory pathway, the number of neurons expressing calretinin was increased indicating that neuronal differentiation was enhanced: newly born neurons occurred within and around the RMS, most of them expressed calretinin and left the pathway starting about 2 weeks after the lesion. Thereafter, these neurons preserving their phenotype, spread for long distances, and accumulated ectopically in dorsal regions of the anterior olfactory nucleus and the frontal cortex. Finally, transplantation of adult subventricular cells into the lesioned pathway showed that the lesion neither prevents neuronal migration nor alters its direction. Thus, although the olfactory bulb appears to regulate the pace of the developmental processes, its disconnection does not prevent the proliferation, migration and phenotypic acquisition of newly generated bulbar interneurons that, since they cannot reach their terminal domains, populate some precise regions of the lesioned adult forebrain.

High incidence of herpes zoster in patients with AIDS soon after therapy with protease inhibitors

A high incidence of herpes zoster was noticed among patients with AIDS, shortly after addition of a protease inhibitor to their baseline treatment with nucleoside analogue reverse-transcriptase inhibitors. Within a median follow-up of 64 weeks (range, 34-103 weeks), 14 patients (7%) had a first episode or a recurrence of herpes zoster (6.2 episodes per 100 patient-years). No episodes of zoster were diagnosed before week 4. Twelve episodes (86%) occurred between weeks 4 and 16. The risk of zoster was independent of age, sex, type of protease inhibitor, and CD4+ lymphocyte count and viral load at baseline and month 1. A CD8+ lymphocyte proportion at baseline of > 66% (hazard ratio [HR], 10.6; 95% confidence interval [CI], 3.4-33.1) and an increase in CD8+ lymphocyte proportion at month 1 of > 5% (HR, 32; 95% CI, 8.1-126.4) were independently associated with the risk of herpes zoster. These data might be clinically useful for determining transient prophylaxis for those patients at high risk.

Semaphorins III and IV repel hippocampal axons via two distinct receptors

The semaphorins are the largest family of repulsive axon guidance molecules. Secreted semaphorins bind neuropilin receptors and repel sensory, sympathetic and motor axons. Here we show that CA1, CA3 and dentate gyrus axons from E15-E17 mouse embryo explants are selectively repelled by entorhinal cortex and neocortex. The secreted semaphorins Sema III and Sema IV and their receptors Neuropilin-1 and −2 are expressed in the hippocampal formation during appropriate stages. Sema III and Sema IV strongly repel CA1, CA3 and dentate gyrus axons; entorhinal axons are only repelled by Sema III. An antibody against Neuropilin-1 blocks the repulsive action of Sema III and the entorhinal cortex, but has no effect on Sema IV-induced repulsion. Thus, chemorepulsion plays a role in axon guidance in the hippocampus, secreted semaphorins are likely to be responsible for this action, and the same axons can be repelled by two distinct semaphorins via two different receptors.

[Cefixime versus amoxicillin plus netilmicin in the treatment of community-acquired non-complicated acute pyelonephritis]

BACKGROUND

Community-acquired non-complicated acute pyelonephritis (APN) is a frequent, occasionally serious infection (around 20% of the cases are bacteremic) that usually requires hospital admission. The third generation oral cephalosporins which are active against more than 95% of E. coli strains should allow the outpatient management of these patients.

OBJECTIVE

To evaluate the bacteriological and clinical efficacy of oral cefixime in comparison to amoxicilin plus netilcilin in the treatment of APN.

PATIENTS AND METHODS

Patients older than 18 years affected by APN were included in a fourteen month prospective study. According to a random numbers chart, the patients received cefixime (400 mg/24 h in a single daily dose for 12 days) or amoxicilin (1 g/8 h per os) plus netilmicin (4 mg/kg/24 h in a single intramuscular daily dose) during five days followed by 7 days of an oral treatment chosen according to the susceptibility pattern of isolated microorganism.

RESULTS

Sixty-one patients received cefixime and 65 amoxicillin plus retilmicin. There were no significant differences between both groups of patients. Thirty-two patients presented bacteremia (25.4%). The mean (SD) eak and trough concentrations of netilmicin were 11.4 (2.8) mg/l and 0.38 (0.4) mg/l, respectively. Clinical response was favorable in 97% of patients treated with cefixime and in 98% of those treated with amoxicilin plus netilmicin (p = NS). The infection recurred in 10 out of 59 patients (16.9%) in the cefixime arm of the study and in 9 out of 64 patients (14%) treated with amoxicillin plus netilmicin (p = NS). Tolerance to the study drugs was good in both arms of the study, and renal function remained normal.

CONCLUSION

Cefixime seems to be an acceptable alternative to the regimens containing an aminopenicillin and an aminoglycoside for the treatment of community-acquired non-complicated APN.

Regional and cellular patterns of reelin mRNA expression in the forebrain of the developing and adult mouse

The reelin gene encodes an extracellular protein that is crucial for neuronal migration in laminated brain regions. To gain insights into the functions of Reelin, we performed high-resolution in situ hybridization analyses to determine the pattern of reelin expression in the developing forebrain of the mouse. We also performed double-labeling studies with several markers, including calcium-binding proteins, GAD65/67, and neuropeptides, to characterize the neuronal subsets that express reelin transcripts. reelin expression was detected at embryonic day 10 and later in the forebrain, with a distribution that is consistent with the prosomeric model of forebrain regionalization. In the diencephalon, expression was restricted to transverse and longitudinal domains that delineated boundaries between neuromeres. During embryogenesis, reelin was detected in the cerebral cortex in Cajal-Retzius cells but not in the GABAergic neurons of layer I. At prenatal stages, reelin was also expressed in the olfactory bulb, and striatum and in restricted nuclei in the ventral telencephalon, hypothalamus, thalamus, and pretectum. At postnatal stages, reelin transcripts gradually disappeared from Cajal-Retzius cells, at the same time as they appeared in subsets of GABAergic neurons distributed throughout neocortical and hippocampal layers. In other telencephalic and diencephalic regions, reelin expression decreased steadily during the postnatal period. In the adult, there was prominent expression in the olfactory bulb and cerebral cortex, where it was restricted to subsets of GABAergic interneurons that co-expressed calbindin, calretinin, neuropeptide Y, and somatostatin. This complex pattern of cellular and regional expression is consistent with Reelin having multiple roles in brain development and adult brain function.

TrkB and TrkC signaling are required for maturation and synaptogenesis of hippocampal connections

Recent studies have suggested a role for neurotrophins in the growth and refinement of neural connections, in dendritic growth, and in activity-dependent adult plasticity. To unravel the role of endogenous neurotrophins in the development of neural connections in the CNS, we studied the ontogeny of hippocampal afferents in trkB (-/-) and trkC (-/-) mice. Injections of lipophilic tracers in the entorhinal cortex and hippocampus of newborn mutant mice showed that the ingrowth of entorhinal and commissural/associational afferents to the hippocampus was not affected by these mutations. Similarly, injections of biocytin in postnatal mutant mice (P10-P16) did not reveal major differences in the topographic patterns of hippocampal connections. In contrast, quantification of biocytin-filled axons showed that commissural and entorhinal afferents have a reduced number of axon collaterals (21-49%) and decreased densities of axonal varicosities (8-17%) in both trkB (-/-) and trkC (-/-) mice. In addition, electron microscopic analyses showed that trkB (-/-) and trkC (-/-) mice have lower densities of synaptic contacts and important structural alterations of presynaptic boutons, such as decreased density of synaptic vesicles. Finally, immunocytochemical studies revealed a reduced expression of the synaptic-associated proteins responsible for synaptic vesicle exocytosis and neurotransmitter release (v-SNAREs and t-SNAREs), especially in trkB (-/-) mice. We conclude that neither trkB nor trkC genes are essential for the ingrowth or layer-specific targeting of hippocampal connections, although the lack of these receptors results in reduced axonal arborization and synaptic density, which indicates a role for TrkB and TrkC receptors in the developmental regulation of synaptic inputs in the CNS in vivo. The data also suggest that the genes encoding for synaptic proteins may be targets of TrkB and TrkC signaling pathways.

Endogenous protein kinase A inhibitor (PKIalpha) modulates synaptic activity

Protein kinase A (PKA) has long been known to be involved in major regulatory mechanisms underlying synaptic plasticity and complex behaviors such as learning and memory. The endogenous PKA inhibitor, PKIalpha, has been extensively studied for its effects on PKA and PKA-mediated signal transduction. Clear functions for PKIalpha in vivo, however, remain to be established. Here we describe that several forms of synaptic stimulation in the rat hippocampus cause a dramatic decrease in the concentration of PKIalpha in dentate granule cells. Furthermore, chronic infusion of antisense oligonucleotides against PKIalpha into the rat brain results in a dramatic reduction of the excitability of these neurons and elimination of their ability to exhibit long-term potentiation (LTP) and long-term depression (LTD), suggesting a stimulus-dependent regulatory role for PKIalpha in PKA signal transduction.

Involvement of distinct pioneer neurons in the formation of layer-specific connections in the hippocampus

During neural development, specific recognition molecules provide the cues necessary for the formation of initial projection maps, which are reshaped later in development. In some systems, guiding cues for axonal pathfinding and target selection are provided by specific cells that are present only at critical times. For instance, the floor plate guides commissural axons in the spinal cord, and the subplate is involved in the formation of thalamocortical connections. Here we study the development of entorhinal and commissural connections to the murine hippocampus, which in the adult terminate in nonoverlapping layers. We show that two groups of pioneer neurons, Cajal-Retzius cells and GABAergic neurons, form layer-specific scaffolds that overlap with distinct hippocampal afferents at embryonic and early postnatal stages. Furthermore, at postnatal day 0 (P0)-P5, before the dendrites of pyramidal neurons develop, these pioneer neurons are preferential synaptic targets for hippocampal afferents. Birthdating analysis using 5'-bromodeoxyuridine (BrdU) pulses showed that most such early-generated neurons disappear at late postnatal stages, most likely by cell death. Together with previous studies, these findings indicate that distinct pioneer neurons are involved in the guidance and targeting of different hippocampal afferents.

The functions of the preplate in development and evolution of the neocortex and hippocampus

Recently, it has been shown that the early developmental organization of the archicortical hippocampus resembles that of the neocortex. In both cortices at embryonic stages, a preplate is present, which is split by the formation of the cortical plate into a marginal zone and a subplate layer. The pioneer neurons of the preplate are believed to form a phylogenetically ancient cortical structure. Neurons in these preplate layers are the first postmitotic neurons and have important roles in the development of the cerebral cortex. Cajal-Retzius cells in the marginal zone regulate the phenotype of radial glial cells and may direct neuronal migration establishing the inside-out gradient of corticogenesis. Furthermore, pioneer neurons form the initial axonal connections with other (sub)cortical structures. A significant difference between the hippocampus and neocortex, however, is that in the hippocampus, most afferents are guided by the pioneer neurons in the prominent marginal zone, while in the neocortex most ingrowing afferent axons enter via the subplate. At later developmental periods, most pioneer neurons disappear by cell death or transform into other neuronal shapes. Here, we review the early developmental organization of the mammalian cerebral cortex (both neocortex and hippocampus) and discuss the functions and fate of pioneer neurons in cortical development, in particular that of Cajal-Retzius cells. Evaluating the developmental properties of the hippocampus and neocortex, we present the hypothesis that the distribution of the main ingrowing afferent systems in the developing neocortex, which differs from the one in the hippocampal region, may have enabled the specific evolution of the neocortex.

[Treatment of pneumonia caused by Legionella with azithromycin]

Nineteen patients with pneumonia caused by Legionella, who did not need to be admitted to ICU were treated with 500 mg/day of azithromycin. The etiological diagnosis was made retrospectively by detecting Legionella pneumophila in the urine of nine patients and/or by serology (seroconversion or single titer 1/256) in 19 cases. None of them met the criteria for ICU admittance nor had received prior treatment with antibiotics which were potentially active against L. pneumophila. Serology tests and radiography of the thorax were carried out on all the patients in the study during their convalescence period. The average age (+/- SD) of the group was 58.5 +/- 16.2 years. The average respiratory frequency (+/- SD) 26 +/- 6 breaths per minute; the radiologic extension was of one lobule in 18 cases and two lobules in one case. No patients showed bilateral disease. Arterial gasometry (FiO2 0.21) showed a pO2 average of (+/- SD) 53 +/- 14 mmHg and the hemogram an average of 6.700 leukocytes/mm3 (range: 4,200-41-800). All the patients progressed favorably. The average duration of fever was 1.8 days; the average stay (+/- SD) was 6.1 +/- 2 days. The treatment was well tolerated. One month after discharge radiographies were clear for all patients. There were no relapses. In conclusion, 3-day administration of azithromycin was found to be a useful guide in the treatment of community acquired pneumonia caused by Legionella in patients whose clinical situation does not require ICU administration and allows for oral administration.

Expression of nerve growth factor and neurotrophin-3 mRNAs in hippocampal interneurons: morphological characterization, levels of expression, and colocalization of nerve growth factor and neurotrophin-3

We have investigated the distribution and morphology of hippocampal interneurons that express the neurotrophins nerve growth factor (NGF) and neurotrophin-3 (NT-3) in the rat. For this study, we combined in situ hybridization for the detection of NGF and NT-3 mRNAs and immunocytochemistry against the calcium-binding proteins parvalbumin (PARV), calretinin (CALR), and calbindin (CALB). Whereas the majority of PARV+ interneurons expressed NGF mRNA, only subsets of CALR- and CALB-immunoreactive interneurons (23% and 24%, respectively) displayed NGF hybridization. Most CALB/NGF+ cells were located in the stratum oriens/alveus of the CA3-CA1 regions, suggesting that they may include the population of CALB+, hippocamposeptal, nonpyramidal neurons. Most of the nonspiny CALR/NGF+ neurons were located within or in the vicinity of the pyramidal layer and had faint CALR immunostaining and stellate, thin dendrites. Regarding the spiny CALR-immunoreactive cells, we found that most of these neurons in the hilus were NGF+, whereas only 59% of displayed NGF hybridization in the stratum lucidum of the CA3 region. A small subset of PARV- and CALR-immunoreactive cells expressed NT-3 mRNA (16% and 13%, respectively). NT-3 message was not found in the large basket cells of the dentate gyrus, whereas the distribution and morphology of CALR/NT-3+ cells were similar to those of nonspiny CALR/NGF+ cells. In fact, double in situ hybridization analysis confirmed that most NT-3+ neurons also expressed NGF mRNA, indicating coexpression of both neurotrophins in subpopulations of PARV+ and CALR+ neurons. Moreover, the level of NGF mRNA expression was higher in PARV+ neurons than in CALR- and CALB-immunoreactive interneurons, whereas NT-3 message was expressed similarly in PARV+ and CALR+ neurons. The present findings show a differential expression of NGF and NT-3 mRNAs in subsets of hippocampal interneurons and suggest that the expression of these transcripts depends on factors intrinsic to particular cell types.

[Chronic enteropathy of unknown etiology in patients with AIDS. An analysis of 40 cases]

BACKGROUND

Data about the etiology of chronic enteropathy in AIDS patients are scarce and are very dependent upon the geographical area. The aim of this study was to detect microorganisms potentially associated with chronic enteropathy in AIDS patients with diarrhoea for more than one month, and initial negative routine stool bacterial cultures and examinations for ova and parasites. The degrees of associated intestinal malabsorption and immunodeficiency were also analysed.

PATIENTS AND METHODS

Forty consecutive patients were recruited from January 1993 to December 1994. The following studies were performed: Intestinal absorption tests (d-xylose and 14C-triolein), CD4/CD8 cell counts, microbiological studies (standard stool cultures for detection of bacteria and examinations for ova and parasites including the detection of Enterocitozoon bieneusi spores by the Weber's stain), upper gastrointestinal endoscopy or colonoscopy with intestinal biopsies and blood cultures for CMV and mycobacteria.

RESULTS

The median duration of diarrhoea was 4 months and the mean weight loss was 8.4 kg. Ninety percent of patients had less than 0.1 x 10(9) CD4+ cells/l, with a mean CD4+ cell count of 0.035 x 10(9)/l. Malabsorption was found in 84% of patients. An etiological diagnosis of chronic enteropathy was reached in 60% of the patients. The yield of pathological examination was 37% and the microbiological test using samples of faeces and blood were positive in 45% and 20% of cases respectively. The most frequently identified microorganisms were CMV (10 cases), E. bieneusi (9), enterobacteria (8), Cryptosporidium parvum (5), Leishmania donovani (2). Patients with enteropathy caused by E. bieneusi had lower count of CD4 cells (p = 0.005) and with higher serum levels of alkaline phosphatase (p = 0.02) than patients with CMV enteropathy.

CONCLUSIONS

Stool Weber's stain and CMV and mycobacterial blood cultures should be added to the standard work-up diagnosis in patients with chronic diarrhoea and a CD4+cells count below 0.1 x 10(9) l. Upper and/or lower gastrointestinal endoscopies with intestinal biopsies should be performed only in patients with persistent diarrhea without microbiological diagnosis or a lack of response to treatment.

Placenta-specific expression of the rat growth hormone-releasing hormone gene promoter in transgenic mice

GH-releasing hormone (GHRH) is a hypothalamic peptide that plays a critical role in controlling the synthesis and secretion of GH in the anterior pituitary. Along with many other hypothalamic hormones, GHRH is also expressed in the placenta, although its physiological role in this tissue has not yet been determined. The placental prepro-GHRH is identical to that found in the hypothalamus. However, the placental and hypothalamic GHRH messenger RNAs differ in the region corresponding to the untranslated exon 1. A combined mechanism involving the use of tissue-specific promoters and the differential splicing of exon 1 generates the mature GHRH messenger RNAs in placenta and hypothalamus. As a first step toward the localization of the regulatory elements involved in the placenta-specific expression of the GHRH gene, we have generated transgenic mice containing constructs in which potential regulatory sequences of the rat GHRH gene were fused to the chloramphenicol acetyltransferase (CAT) reporter gene. Construct GHRH-CAT1, which contains 7.5 kilobases of flanking sequences upstream to the placental transcription start site, did not promote CAT expression in the transgenic animals. In contrast, construct GHRH-CAT2, which differs from construct GHRH-CAT1 in having additional sequences located downstream to placental exon 1, exhibited high levels of CAT expression in brain and placenta. Our results show that the sequences included in construct GHRH-CAT2 contain the cis-acting regulatory elements necessary to direct developmentally regulated and cell type-specific expression of the CAT gene in the placenta. Unexpectedly, the expression of the transgene in the brain was detected in glial cells of different areas, but not in the hypothalamus.

Cortistatin is expressed in a distinct subset of cortical interneurons

Cortistatin is a presumptive neuropeptide that shares 11 of its 14 amino acids with somatostatin. In contrast to somatostatin, administration of cortistatin into the rat brain ventricles specifically enhances slow wave sleep, apparently by antagonizing the effects of acetylcholine on cortical excitability. Here we show that preprocortistatin mRNA is expressed in a subset of GABAergic cells in the cortex and hippocampus that partially overlap with those containing somatostatin. A significant percentage of cortistatin-positive neurons is also positive for parvalbumin. In contrast, no colocalization was found between cortistatin and calretinin, cholecystokinin, or vasoactive intestinal peptide. During development there is a transient increase in cortistatin-expressing cells in the second postnatal week in all cortical areas and in the dentate gyrus. A transient expression of preprocortistatin mRNA in the hilar region at P16 is paralleled by electrophysiological changes in dentate granule cells. Together, these observations suggest mechanisms by which cortistatin may regulate cortical activity.

TrkB signaling is required for postnatal survival of CNS neurons and protects hippocampal and motor neurons from axotomy-induced cell death

Newborn mice carrying targeted mutations in genes encoding neurotrophins or their signaling Trk receptors display severe neuronal deficits in the peripheral nervous system but not in the CNS. In this study, we show that trkB (-/-) mice have a significant increase in apoptotic cell death in different regions of the brain during early postnatal life. The most affected region in the brain is the dentate gyrus of the hippocampus, although elevated levels of pyknotic nuclei were also detected in cortical layers II and III and V and VI, the striatum, and the thalamus. Furthermore, axotomized hippocampal and motor neurons of trkB (-/-) mice have significantly lower survival rates than those of wild-type littermates. These results suggest that neurotrophin signaling through TrkB receptors plays a role in the survival of CNS neurons during postnatal development. Moreover, they indicate that TrkB receptor signaling protects subpopulations of CNS neurons from injury- and axotomy-induced cell death.

[Yield of blood cultures in relation to the cultured blood volume in Bactec 6A bottles]

BACKGROUND

Concentration of microorganisms in blood is low in bacteremia from extravascular sources. The best yield from blood cultures is achieved by culturing a minimum of 10-20 ml, although in some processing blood culture systems such as Bactec NR-860, smaller volume is used. The objectives of the present study were to establish the frequency in which inadequate small blood volumes are employed for culturing and to analyze the relation between the cultured blood volume in Bactec 6A bottles and the yield achieved.

MATERIAL AND METHODS

We weighed 2000 Bactec 6A bottles pertaining to consecutive blood cultures obtained from untreated patients with clinical suspicion of Infection. The cultured blood volume was estimated subtracting the mean empty bottle weight.

RESULTS

Microorganisms were recovered from 251 bottles (12.5%). One hundred and thirty one (6.8%) isolates were considered as clinically significant and 115 (5.7%) as contaminant. The inoculated blood volume in both significant (5.532 +/- 1.587 ml) and non-significant (5.471 +/- 1.563 ml) recoveries was superior than that of bottles without microbiologic growth (5.209 +/- 1.575 ml, p = 0.016 and p = 0.06, respectively). A linear positive trend was found between the cultivated blood volume and the rate of recoveries (p = 0.008). Within the range of 1 up to 10 ml, the rate of recoveries increased 2.28% for each additional ml of cultivated blood (r = 0.953, p < 0.0001). Out of the 2,000 weighed bottles 127 (6.3%) contained less than 3 ml of blood and 576 (29%) between 3 and 5 ml.

CONCLUSIONS

We have proved that the rate of recoveries from Bactec 6A bottles increased with the volume of cultured blood. In untreated patients, this increase is maintained up to volumes of 7 to 10 ml.

Risk factors for oxacillin/methicillin resistance in coagulase-negative staphylococci

The clinical variables associated with isolation of oxacillin- and methicillin-resistant, coagulase-negative staphylococci (CNS) from blood cultures of hospitalized patients were studied. One hundred CNS strains (49 oxacillin-susceptible; 51 oxacillin-resistant) isolated consecutively from one of two or more sets of blood cultures were collected. Only two variables were independently associated with recovery of oxacillin/methicillin-resistant strains by a multivariate analysis: length of hospital stay > 10 days (OR 5.2, 95% CI = 1.7-15.7), and administration of antimicrobial agents in the previous 14 days (OR 4.5, 95% CI = 1.7-11.7). Analysis of the antibiotics administered indicated that only beta-lactams were associated with a statistically significant risk of resistance to oxacillin/methicillin (OR of beta-lactams vs no antibiotics = 6.94, 95% CI = 1.9-25.3; OR of non-beta-lactams vs no antibiotics = 2.64, 95% CI = 0.8-8.3). Length of hospital stay (especially > 10 days) and prior administration of antimicrobial agents (mainly beta-lactams) independently predicted the presence of oxacillin/methicillin-resistant CNS in blood cultures.

Cajal-Retzius cells regulate the radial glia phenotype in the adult and developing cerebellum and alter granule cell migration

Studies on the reeler mutation have shown that pioneer Cajal-Retzius (CR) cells are involved in neuronal migration in the developing cortex. Here, we use grafting and coculture experiments to investigate the mechanisms by which CR cells govern migration. We show that transplantation of embryonic CR cells, but not other cortical neurons, into adult cerebella induces a transient rejuvenation of host Bergmann glia into a radial glia phenotype. Similarly, CR cells sustain the phenotype of developing radial glia in postnatal cerebellar slices and induce the organization of a glial scaffold inside the CR cell explants. Studies with semipermeable inserts show that these effects are mediated by diffusible signals. We also show that CR cells adjacent to the surface of cerebellar slices reverse the direction of the migration of granule cells. Finally, CR cells from reeler mutant embryos elicited similar effects. These observations imply a role for CR cells in the regulation of the radial glia phenotype, a key step for neuronal migration, and suggest that these pioneer neurons may also exert a chemoattractive influence on migrating neurons.

[Prophylaxis secondary to retinitis by CMV in patients with AIDS: the efficacy of an intermittent schedule of 3 days/week]

BACKGROUND

An approach of daily or 5 days per week treatment as maintenance therapy is mandatory among HIV patients with CMV retinitis. We evaluate the efficacy and tolerance of thrice weekly maintenance therapy for CMV retinitis in AIDS patients.

METHODS

Sixty nine consecutive patients with CMV disease were eligible for a prospective open clinical trial. Thirty three completed the induction treatment of CMV retinitis, agreed on maintenance thrice weekly and were included. Twenty nine received Ganciclovir (10 mg/kg/day) and 4 foscarnet (100 mg/kg/day) thrice weekly.

RESULTS

The mean age was 34 years. Twenty nine of the 33 (87%) were males and 13 (39%) drug addicts. Mean CD4+ lymphocyte count at inclusion was 44 cells per relapsed and 22 (66%) died. The median time to relapse, survival free of CMV retinitis and the median survival was 18, 14 and 34 weeks respectively.

CONCLUSION

Since the outcome of our patients with thrice weekly maintenance therapy was similar to historical controls our study at least provides the rational for this hypothesis to be tested in a future randomised trial.

A role for Cajal-Retzius cells and reelin in the development of hippocampal connections

During development of the nervous system, specific recognition molecules provide the cues necessary for the formation of neural connections. In some regions, guiding cues for axonal pathfinding and target selection are provided by specific cells that exist only transiently during development, such as the floorplate or the cortical subplate. In the hippocampus, distinct groups of fibres innervate different layers. We have tested the hypothesis that transient neurons in the hippocampus provide positional information for the targeting of these fibres. Here we report that ablation of Cajal-Retzius cells in organotypic slice cultures of hippocampus prevented the ingrowth of entorhinal but not of commissural afferents. Experiments inhibiting Reelin (an extracellular matrix protein expressed by Cajal-Retzius cells) and analysis of reeler mutant mice showed dramatic abnormalities in the development of entorhinal afferents. Thus Cajal-Retzius cells and reelin are essential for the formation of layer-specific hippocampal connections.

Survival of Cajal-Retzius cells after cortical lesions in newborn mice: a possible role for Cajal-Retzius cells in brain repair

Transient Cajal-Retzius (CR) cells in layer I of the mammalian cerebral cortex are the first postmitotic neurons and they are believed to play a role in neuronal migration and lamination during cortical development. Freezing insults to the cortex of newborn mice produce cortical malformations similar to those observed in human brain disorders. Here we have used calretinin immunostaining to investigate the response of CR cells to freezing lesions of the cortical surface. Shortly after injury, CR cells disappeared from the lesioned zone. Moreover, CR cells located near the lesioned area adopted extremely fusiform shapes. At later postnatal stages (P12), CR cells were still abundant in layer I of the lesioned zone, in contrast to their almost complete loss in control animals. These results show that CR cells survive for longer developmental periods following cortical injury. Furthermore, the initial loss and later re-appearance of CR cells suggest that these neurons might migrate tangentially from the cortical areas surrounding the lesioned zone. These findings imply a role for CR cells in brain repair after cortical injury during development.

Degeneration of Cajal-Retzius cells in the developing cerebral cortex of the mouse after ablation of meningeal cells by 6-hydroxydopamine

In the central nervous system, the neurotoxic drug 6-hydroxydopamine (6-OHDA) selectively deletes central catecholaminergic neurons and meningeal cells. Meningeal cells are known to contribute to brain development and their specific degeneration leads to disorganized neuronal positioning. We have analyzed whether a particular population of cortical pioneer neurons, the Cajal-Retzius (CR) cells, which lie just below meningeal cells, is also affected by 6-OHDA treatment. We show that application of 6-OHDA to the cortical surface leads to a rapid degeneration of CR cells, without affecting other cortical neurons. The ablation of CR cells was prevented by normetanephrine, which blocks the 6-OHDA uptake into meningeal cells. These results indicate that the disappearance of CR cells after 6-OHDA treatment may be a result of the ablation of the meningeal cells and suggest a trophic dependence of CR cells upon meningeal cells.

Regional variability and postsynaptic targets of chandelier cells in the hippocampal formation of the rat

Chandelier cells are specialized cortical GABAergic neurons that establish synaptic contacts exclusively with the axon initial segments of principal neurons. They are found in all regions of the hippocampal formation. Here we describe their morphological features in the hilus and in regions CA1 and CA3 by using Golgi/electron microscopy. Attempts were also made to identify the target neurons of chandelier cells in the hilus and entorhinal cortex. Golgi-impregnated chandelier cells display a complex axonal arbor in CA1, with many collaterals forming strings of boutons. The axon plexuses of such cells are less developed in CA3, whereas those in the hilus cover the entire region, although single collaterals are rather simple, with only a few boutons. The dendrites of chandelier cells in CA1 and CA3 have an orientation similar to that of pyramidal cell dendrites and are thus likely to be activated by the same afferent fiber systems. The hilar chandelier cells do not give rise to dendrites invading the molecular layer. Thus, these cells may not receive a dense input from the entorhinal cortex but may be driven by the abundant mossy fiber collaterals in the hilar region. In the CA1 and CA3 regions, the axons of chandelier cells contact the axon initial segments of pyramidal cells. In the hilar region, gold-toned boutons were found to impinge on the initial segments of neurons displaying characteristics of mossy cells. This notion was substantiated by electron microscopic analysis of mossy cells identified by intracellular injection of Lucifer yellow. Those cells regularly showed numerous symmetric synapses on their axon initial segments. Entorhinohippocampal projection cells, identified by injection of horseradish peroxidase into the hippocampus, were found to be preferential targets of chandelier cells in the entorhinal cortex. Our data point to regional variations in chandelier cell morphology and connectivity and indicate that chandelier cells are a principal component of inhibitory mechanisms in all stations of the main excitatory pathway of the hippocampal formation.

[In vitro effect of heroin on neutrophil polymorphonuclear leukocytes from peripheral blood]

BACKGROUND

Infections are the most common medical complications in drug addicts. Some studies suggest that heroin itself could facilitate them by altering the polymorphonuclear leukocyte (PMNL) function of these patients. The aim of this study was to analyze the heroin effect on the chemotaxis, the phagocytosis and the bactericidal oxidative metabolic activity on PMNL from 10 healthy adults.

MATERIAL AND METHODS

Three samples of 20 ml of blood were obtained from each donor, separating the leukocytes later. The first sample was used as control (A group); heroin was added to the blood of the second sample before PMNL separation (1 mg of heroin into 20 ml of blood)(B group) and to the third sample after PMNL separation (0.05 mg of heroin in 1 ml of PMNL suspension)(C group). The concentration of heroin used was 50 microliters/ml of blood (this concentration was higher than the lethal concentration found in the blood of drug addicts who die from heroin overdose). The PMNL functions studied in vitro were the chemotaxis of PMNL applying the under agarosa gel method, and for the phagocytosis and the intracellular oxidative metabolic activity the following two tests were used: the ingestion of bacto-latex particles combined with nitroblue tetrazolium (NBT) reduction test and the chemoluminiscence method. The statistical analysis was done using parametric and non-parametric tests.

RESULTS

There were no differences between the three groups studied (A, B or C) regarding chemotaxis, the ingestion of bacto-latex particles and the NBT reduction test. Concerning chemoluminiscence, it was inferior in the C group (with PMNL directly incubated with heroin) compared with A group (control) and B group (with PMNL from blood with heroin)(p < 0.05). However, there were no statistically significant differences between A and B groups.

CONCLUSIONS

In this study, heroin did not have any in vitro significative effect of chemotaxis, phagocytosis and oxidative metabolic activity on the human PMNL.

Differential survival of Cajal-Retzius cells in organotypic cultures of hippocampus and neocortex

Cajal-Retzius (CR) cells are transient, pioneer neurons of layer I of the cortex that are believed to play essential roles in corticogenesis, e.g., in neuronal migration and synaptogenesis. Here we have used calretinin immunostaining to study the characteristics, survival, and fate of CR cells in single organotypic slice cultures of mouse neocortex and hippocampus deprived of their extrinsic afferents. In neocortical explants, CR cells were observed after 1-3 d in vitro (DIV), but they disappeared after 5-7 DIV, which is similar to their time of degeneration in vivo. The disappearance of CR cells in neocortical slices was prevented by incubation with tetrodotoxin and the glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3,-dione but not by 2-amino-5-phosphonopentanoic acid, suggesting that neuronal activity and non-NMDA glutamate receptors may trigger CR cell death in the neocortex. In contrast to the situation in vivo, in which many hippocampal CR cells disappear at approximately the third postnatal week, CR cells survived in single hippocampal cultures after long incubation times (31 DIV), with their morphology essentially unaltered. In contrast, fewer CR cells were found when hippocampal slices were cocultured with explants from the entorhinal cortex. Because CR cells are transient synaptic targets for entorhinohippocampal afferents, these findings suggest a role for entorhinal afferents in the degeneration of CR cells in the hippocampus. In conclusion, this study shows different survival properties of CR cells in organotypic slice cultures of hippocampus and neocortex, and it suggests that different mechanisms are involved in the regulation of the process of naturally occurring CR cell death in the two cortical regions.

Epidemiology and outcome of Pseudomonas aeruginosa bacteremia, with special emphasis on the influence of antibiotic treatment. Analysis of 189 episodes

OBJECTIVE

To evaluate the trend in incidence of Pseudomonas aeruginosa bacteremia, underlying conditions of patients, mortality rate, and factors associated with poor outcome.

PATIENTS AND METHODS

Medical charts of 189 consecutive episodes of P aeruginosa bacteremia, detected between January 1, 1991, and December 31, 1994, were prospectively evaluated. Associated risk factors, treatment, and outcome were recorded.

RESULTS

Pseudomonas aeruginosa bacteremia represented 5.7% of the total number of bacteremias, 6.9% of nosocomial bacteremias, and 23.6% of nosocomial gram-negative bacteremias. There were 1.5 episodes per 1000 discharges. These numbers were slightly lower than those recorded at our hospital 10 years earlier. Human immunodeficiency virus infection was the most frequent underlying disease (28/189 [15%]). Overall mortality was 18% (34/189). The presence of fatal underlying disease (P < .001), surgery (P = .001), pneumonia (P = .02), and severe sepsis (P < .001) were associated with poor prognosis, the mortality of the patients with these variables being 28%, 28%, 47%, and 62%, respectively. The presence of inappropriate definitive antimicrobial treatment became an independent factor predictive of death (P = .04) only when the subset of patients with intravenous catheter-associated bacteremia was excluded from the analysis. The survival rate was no greater in patients who received 2 or more antibiotics active in vitro against P aeruginosa than in those who received only 1. Neutropenia was not associated with increased mortality. The use of colony-stimulating factors did not affect the outcome of the neutropenic patients.

CONCLUSIONS

The rate of P aeruginosa bacteremia is falling slightly at our hospital. The emergence of the human immunodeficiency virus epidemic has had a considerable impact on both epidemiology and mortality. The presence of severe underlying disease, surgery, pneumonia, and, especially, severe sepsis are associated with a poor outcome. With the exclusion of patients with intravenous catheter-associated P aeruginosa bacteremia, the administration of an appropriate antimicrobial therapy is essential to a good outcome. Treatment with 1 active antibiotic seems to be sufficient.

Upregulation of BDNF mRNA expression in the barrel cortex of adult mice after sensory stimulation

Upregulation of brain-derived neurotrophic factor (BDNF) mRNA expression by neuronal activity has been reported in cultured hippocampal cells and in different in vivo excitotoxic paradigms. The aim of the present study was to determine whether sensory stimulation of the whisker-to-barrel pathway alters BDNF mRNA expression in the cortex and, if so, to evaluate the specificity of this effect. To this end, a set of mystacial whiskers was unilaterally stimulated by mechanical deflection, and the expression of BDNF mRNA was analyzed in the barrel cortex by in situ hybridization (ISH) using a 35S-labeled antisense BDNF riboprobe and emulsion autoradiography. A clear-cut and specific upregulation of the BDNF mRNA expression was found at the level of the somatosensory cortex after the increased peripheral stimulation. In the barrel cortex of control mice, BDNF mRNA was present in a few cells in layers II/III and VI, whereas it was almost undetectable in layer IV. After 6 hr of whisker stimulation, increased levels of BDNF mRNA were found in layers II to VI of the contralateral barrel cortex. In layer IV, BDNF upregulation was confined to the barrels corresponding to the stimulated follicles. ISH combined with immunocytochemistry against the three calcium-binding proteins parvalbumin, calretinin, and calbindin-D28K revealed that BDNF mRNA-expressing cells do not belong to the GABAergic cell population of the barrel cortex. The present results support a role for BDNF in activity-dependent modifications of the adult cerebral cortex.

Transient colocalization of parvalbumin and calbindin D28k in the postnatal cerebral cortex: evidence for a phenotypic shift in developing nonpyramidal neurons

In the adult rat cerebral cortex the calcium-binding proteins parvalbumin and calbindin D28k are present in essentially non-overlapping populations of GABAergic interneurons. These proteins follow different developmental patterns in the cortex: calbindin D28k-immunoreactive nonpyramidal neurons are abundant until the second postnatal week and decrease markedly thereafter; it is at this time that parvalbumin immunoreactivity develops in cortical nonpyramidal neurons. To determine whether parvalbumin-immunoreactive neurons derive from calbindin D38k positive cells we used double-immunofluorescence studies for both calcium-binding proteins, together with combined immunocytochemistry for calbindin D28k and in situ hybridization for parvalbumin mRNA during postnatal development. Double-labelled cells were found in all cortical layers between P9 and P21, coinciding with the onset of parvalbumin expression. The percentage of colocalization of the two calcium-binding proteins depended on the age and layer examined. Colocalization reached a peak (80-100%) during the second postnatal week. Double-labelled neurons were rare in layer V at all ages studied. The present results indicate a phenotypic shift during the development of some cortical interneurons that halts the expression of calbindin D28k while parvalbumin expression starts. These findings agree with lineage analyses reporting that different types of nonpyramidal neuron arise from a common progenitor.

Thalamic and basal forebrain afferents modulate the development of parvalbumin and calbindin D28k immunoreactivity in the barrel cortex of the rat

In the adult barrel cortex of the rat the calcium-binding proteins calbindin D28k (CALB) and parvalbumin (PARV) are found in separate populations of GABAergic nonpyramidal neurons. In layers II to IV of the barrel cortex most PARV-immunoreactive neurons are likely to derive from a subpopulation of CALB-immunoreactive neurons whose CALB immunoreactivity ceases when they begin to express PARV between the second and third postnatal weeks. The aim of this study was to investigate the influence of subcortical afferents on the neurochemical differentiation of cortical PARV- and CALB-immunoreactive nonpyramidal neurons during development of the barrel cortex. We produced unilateral excitotoxic lesions with a single injection of ibotenic acid (0.5 microl, 0.05 M) in different subcortical nuclei in 7- to 8-day-old rats. Lesions involving the ventroposterior thalamic nuclei resulted in delayed development of PARV and CALB immunoreactivity in the barrel cortex. One week after ibotenic acid injections a transient decrease in the number of PARV-immunoreactive neurons in layer IV was observed, together with increased numbers of CALB-immunoreactive neurons in all cortical layers. The number of nonpyramidal neurons displaying coexistence of PARV and CALB in the lesioned hemisphere also increased compared with the numbers in the control hemisphere or control littermates. In contrast, lesions affecting the globus pallidus, zona incerta and reticular thalamic nucleus transiently increased the number of PARV-immunoreactive neurons in layers II and III, but had no effect on the number of CALB-positive cells. From 3 weeks onwards no differences were found between control and lesioned hemispheres after injections into either the ventroposterior thalamic nuclei or the magnocellular basal forebrain. These results suggest that CALB and PARV expression in nonpyramidal cortical neurons can be reversibly modulated in opposite directions by different cortical afferents during postnatal development.

Expression of NGF and NT3 mRNAs in hippocampal interneurons innervated by the GABAergic septohippocampal pathway

We used in situ hybridization for the detection of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT3) mRNAs combined with immunocytochemistry against the calcium-binding proteins parvalbumin (PARV), calbindin 28k (CALB), and calretinin (CALR) to determine the expression of neurotrophins in functionally distinct subsets of hippocampal interneurons. Most PARV-immunoreactive neurons in the hippocampus were NGF mRNA-positive (82%), which corresponds to 71% of NGF-positive neurons in the hippocampus proper and in the dentate gyrus (excluding granule cells). In contrast, only a subset of CALB- and CALR-immunoreactive interneurons (24% and 23%, respectively) displayed hybridization signals for NGF. Small subsets of PARV- and CALR-positive cells expressed NT3 mRNA, but we did not find hippocampal interneurons expressing BDNF mRNA. These results show that NGF and NT3 genes are differentially regulated in distinct subsets of GABAergic cells, and these interneurons are a major source of NGF production in the hippocampus. We also addressed whether hippocampal interneurons expressing neurotrophins were targets of the GABAergic septohippocampal pathway. We developed a triple-labeling method that combines anterograde tracing of this pathway by means of Phaseolus vulgaris leucoagglutinin injections, with in situ hybridization for the detection of neurotrophins, and immunocytochemistry for calcium-binding proteins. Virtually every PARV-positive neuron innervated by GABAergic septohippocampal baskets expressed NGF mRNA (86%), whereas 39-59% of CALR- and CALB-positive interneurons that were contacted by GABAergic septohippocampal axons showed NGF gene expression. A small subset of NT3 mRNA-expressing interneurons was also innervated by septohippocampal baskets. These findings show that the GABAergic septohippocampal pathway preferentially terminates on interneurons expressing NGF mRNA, suggesting that this neurotrophic factor might be involved in the specification of this connection and in its maintenance and normal function in the adult brain.

[Pneumocystis carinii pneumonia in the transplant recipient]

BACKGROUND

The aim of the present was to study the clinical characteristics and prognostic factors of 20 cases of pneumonia by Pneumocystis carinii (NPC) diagnosed over the last 10 years in renal, renopancreatic, liver and bone marrow transplant recipients.

METHODS

The clinical histories of all the patients transplanted in the authors' hospital from 1985 to 1994 who developed NPC were analyzed. Diagnosis was established by visualization of cysts in methenamine silver staining of bronchialveolar lavage (BAL) samples.

RESULTS

The global incidence of NPC in our transplant population was 1%. However, the incidence was 3% in the recipients who did not receive prophylaxis. No patient in this series received prophylaxis at the time of diagnosis. Ninety percent of the patients had history or rejection. Pneumonia was observed in 15 (75%) in the first 6 months post transplantation. The mean length of the symptoms prior to diagnosis was 10 days. Ninety-five percent of the patients presented cough, dysnea and fever. Radiology demonstrated diffuse alveolointerstitial infiltrates in 18 patients (90%). Basal arterial PO2 was lower than 60 mmHg in 14 (70%) patients and the alveoloarterial gradient of oxygen was greater than 60 mmHg in 9 (45%). Mechanical ventilation was required in 50% of the patients. BAL demonstrated cytologic alterations compatible with CMV infection in 50% of the cases and in two Aspergillus fumigatus was associated. Mortality was 35%. The only variable significantly associated with bad prognosis was the need for mechanical ventilation (p = 0.003).

CONCLUSIONS

The incidence of pneumonia by P. carinii in a population of transplant recipients was 1%. No patient received primary prophylaxis at the time of diagnosis. Most of the episodes were observed during the first 6 months post transplant. Mortality was 35% with the only variable with prognostic significance being the need for mechanical ventilation.

[Analysis of 1,187 consecutive cases of AIDS: variations and trends in time]

BACKGROUND

The characteristics of AIDS patients in Spain have already been described, as have the factors which may or may not be present at the time of AIDS diagnosis influence in the prognosis. The introduction of zidovudine and later other antiretroviral drugs have improved the prognosis versus historical controls. Nonetheless, advances in prevention, control and the treatment of opportunistic infections have provided the greatest influence in the development of clinical manifestations of AIDS: The aim of the present was to study the evolution of AIDS patients seen at the Hospital Clínic in Barcelona, Spain, from 1985 to 1992 and analyze the variations in the time of clinical manifestations and survival.

METHODS

The clinical records of 1187 patients in the Hospital Clinic in Barcelona with HIV infection who developed AIDS (1985-1992) according to the CDC criteria of August 1987 were retrospectively reviewed.

RESULTS

Out of the 1187 AIDS cases, the percentage of women rose from 8% to 25%. The route of HIV infection which has most varied over time has been that of heterosexual relations (68%). Despite being the most frequent form of AIDS presentation, opportunistic infection has decreased from 79% to 51%. Tuberculosis, pneumonia by Pneumocystis carinii and cerebral toxoplasmosis as forms of presentation have also decreased on performing routine primary prophylaxis for these opportunistic infections. A significant trend towards improvement in survival over time was observed, mainly due to better prognosis of patients in whom AIDS diagnosis was obtained due to pneumonia by P. carinii or Kaposi's sarcoma.

CONCLUSIONS

There has been an increase in the percentage of women and heterosexual transmission in AIDS, as well as an important change in the form of AIDS presentation probably due to the systematic administration of primary prophylaxis for several opportunistic infections. There has also been a global improvement in survival.

A pilot case-control study of zidovudine compared with zidovudine plus didanosine in patients with advanced HIV-1 disease and no previous experience with antiretrovirals

Although zidovudine (ZDV) is effective in HIV-1-infected patients, the duration of its efficacy may be short when treatment is started in advanced HIV disease. This pilot prospective case-control study was designed to evaluate the combination of ZDV plus didanosine [ddI] compared with ZDV monotherapy as an initial therapeutic strategy. 'Control' patients (ZDV monotherapy) were matched with 'case' patients (ZDV plus ddI combination therapy) according to the presence or absence of AIDS-defining criteria at entry and CD4 cell count. The case patient group consisted of 35 consecutive HIV-1-infected individuals with < or = 300 CD4 cells/mm3, no previous experience of antiretroviral therapy and who accepted treatment with a combination of ZDV plus ddI. The control patient group consisted of 35 consecutive patients with similar characteristics, but who preferred to start treatment with ZDV alone. Control patients received 250 mg ZDV bid and case patients received ZDV at the same dose plus ddI (200 mg bid). Primary study endpoints were virological (serum HIV-1 RNA) and immunological (CD4 cell count) responses. Viral phenotype (syncytium-inducing (SI) or non-syncytium-inducing (NSI)), development of mutations at codons 215, 41 and 74 and clinical progression (new AIDS-defining event or death) were also assessed. Virological and CD4 cell count responses were significantly greater and more sustained in the group treated with ZDV plus ddI than in the control group, with peak responses of -1.2 +/- 0.7 log10 versus -0.3 +/- 0.4 log10 at 1 month (P = 0.0003) and 61 +/- 52 cells/mm3 versus 19 +/- 25 cells/mm3 at 2 months (P = 0.001), respectively. In both groups the percentage of patients developing a mutation at codon 215 was around 80 per cent at 12 months. A mutation at codon 74 was detected in 30 per cent of case patients at 12 months. Five case patients (14 per cent) versus 12 control patients (34 per cent) showed signs of clinical progression (P = 0.09). In a multivariate model, clinical progression was significantly associated with a baseline

Molecular heterogeneity of progenitors and radial migration in the developing cerebral cortex revealed by transgene expression

We have analyzed the developmental pattern of beta-galactosidase (beta-gal) expression in the cerebral cortex of the beta 2nZ3'1 transgenic mouse line, which was generated using regulatory elements of the beta 2-microglobulin gene and shows ectopic expression in nervous tissue. From embryonic day 10 onward, beta-gal was expressed in the medial and dorsal cortices, including the hippocampal region, whereas lateral cortical areas were devoid of labeling. During the period of cortical neurogenesis (embryonic days 11-17), beta-gal was expressed by selective precursors in the proliferative ventricular zone of the neocortex and hippocampus, as well as by a number of migrating and postmigratory neurons arranged into narrow radial stripes above the labeled progenitors. Thus, the transgene labels a subset of cortical progenitors and their progeny. Postnatally, radial clusters of beta-gal-positive neurons were discernible until postpartum day 10. At this age, the clusters were 250 to 500 microns wide, composed of neurons spanning all the cortical layers and exhibiting several neuronal phenotypes. These data suggest molecular heterogeneity of cortical progenitors and of the cohorts of postmitotic neurons originating from them, which implies intrinsic molecular mosaicism in both cortical progenitors and developing neurons. Furthermore, the data show that neurons committed to the expression of the transgene migrate along very narrow, radial stripes.

Development of calretinin immunoreactivity in the neocortex of the rat

The prenatal and postnatal development of calretinin (CR)-containing elements in the neocortex of the rat was analyzed using immunohistochemistry. CR immunoreactivity in the cortical anlage appeared early at embryonic day 14 (E14), with CR-positive neurons located in the primitive plexiform layer and in the emerging subplate and marginal zones. At later prenatal and early postnatal stages, these two layers showed the highest CR immunostaining in the cortex, and large numbers of cell bodies and fibers were immunostained. From postnatal day 3 (P3) onwards, CR immunostaining disappeared progressively from the subplate-layer VIb and the marginal zone-layer I, so that very few cells remained stained in these layers in the adult. In the cortical plate and prospective layers VIa to II-III, CR-positive neurons were seen at prenatal stages, their numbers increasing markedly during the first postnatal week. Most neurons showed undifferentiated nonpyramidal shapes, and matured during the second and third postnatal weeks, when the adult pattern of CR immunostaining was achieved. In addition, some pyramidal-like neurons in the infragranular layers and in layer II-III transiently expressed CR during the postnatal period, most notably between P3 and P12. Colocalization experiments performed at P0-P3 with antibodies against the neurotransmitter gamma-aminobutyric acid (GABA) showed that most nonpyramidal CR-positive neurons in the derivates of the cortical plate were also GABAergic during development. In contrast, large numbers of CR-containing neurons in the subplate and marginal zone were GABA-negative. The present results show that in addition to recording the early development of a subset of nonpyramidal neurons, CR is transiently expressed in certain GABA-negative populations of the subplate and marginal zone, and most likely in pyramidal neurons.

Calretinin-immunoreactive neurons in the normal human temporal cortex and in Alzheimer's disease

Calretinin-containing neurons (CR) were visualized by immunocytochemistry in the human temporal cortex. The morphology of calretinin-positive neurons ranged from bipolar, bitufted, fusiform to double bouquet cells, whose long axis was parallel to the radial axis of the cortex. Calretinin-immunoreactive cells were more abundant in layers II, III and less frequent in layer VI and white matter. In layer I, large horizontal neurons resembling Cajal-Retzius cells were observed. Layers IV and V contained few labeled cells. The CR-immunoreactive neuropil was abundant, especially in supragranular layers. However, the most prominent feature of the pattern of calretinin staining was the presence of long, vertically oriented bundles of calretinin-immunoreactive processes. These bundles formed a widespread, regular columnar system descending throughout layers II to VI. Despite the virtually identical morphological features of CR-immunoreactive neurons and certain calbindin-immunoreactive neurons, colocalization studies for both antibodies against calretinin and calbindin, revealed little coexistence (in supragranular layers) or none (in infragranular layers). Thus, double bouquet cells could be considered as forming a chemically heterogeneous neuronal population. In addition, four brains from patients with Alzheimer's disease were immunostained for calretinin. No major differences from normal brains were found; the distribution, morphology and the characteristic, vertically oriented bundles resembled those described in normal brains. These data suggest that these calcium-binding protein-containing interneurons are present in normal human brain and that they are resistant to degeneration in Alzheimer's disease.

Developmental expression of parvalbumin mRNA in the cerebral cortex and hippocampus of the rat

Parvalbumin (PARV) belongs to the family of calcium-binding proteins bearing the EF hand domain. Immunocytochemical studies in the cerebral cortex have demonstrated that neurons containing PARV include two types of GABAergic interneurons, namely, basket and axo-axonic chandelier cells. The present study examines the onset and pattern of PARV mRNA expression during the development of rat neocortex and hippocampus by means of 'in situ' hybridization with an oligonucleotide probe corresponding to rat PARV cDNA. In animals aged P0-P6 no signal was detected above background in neocortex or hippocampus. At P8, a few cortical cells displayed a number of silver grains just above background levels. By P10 PARV mRNA-expressing cells in the neocortex were detected almost exclusively in layer V of somatosensory, frontal and cingulate cortices. At P12 PARV mRNA was mainly detected in layers IV, V and VIa. By P14 there was a marked overall increase in the entire neocortex, including layer II-III, both in the number of cells and in their intensity of labelling. Further maturation in the pattern of PARV mRNA concentration was observed between P16 and P21. In the hippocampus low hybridization was observed at P10-P12. In subsequent stages both the number of positive cells and the intensity of labelling increased steadily. No clear-cut radial gradients for the expression of PARV mRNA were observed in the hippocampal region. Our results show that the developmental radial gradient followed by PARV mRNA expression in the neocortex does not follow an 'inside-out' gradient, consistent with previous immunocytochemical findings. Taken together, these data indicate that the developmental sequence followed by the PARV protein directly reflects mRNA abundance and suggest that PARV mRNA expression correlates with the functional maturation of cortical interneurons.

Frequency of autoantibodies to a major epitope on the carboxyl terminal fragment of CENP-B in patients with autoimmune disease

The carboxyl-terminal fragment of CENP-B contains a major epitope for anti-centromere antibodies (ACA). We have developed an enzyme-linked immunoassay (ELISA) for measuring antibodies to the 147-carboxyl-terminal amino acids of CENP-B expressed as a beta-galactosidase fusion protein. The ELISA was 98% sensitive and 95% specific for detecting ACA in a population which included 46 patients with ACA detected by other means. Therefore, the CENP-B ELISA should prove a valuable tool in screening for ACA in populations at risk of developing systemic sclerosis, such as those with Raynaud's phenomenon. Levels of anti-CENP-B antibodies were not increased in unaffected relatives of probands with ACA.

Migrating neurons in the developing cerebral cortex of the mouse send callosal axons

The presence of migrating callosal neurons during the development of the murine cerebral cortex was studied using biocytin and the lipophilic dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate as retrograde tracers. After injections of biocytin in the presumptive somatosensory cortex of newborn mice which were analysed one day later, many anterogradely labelled fibres coursed towards the contralateral hemisphere through the corpus callosum. Retrogradely labelled callosal cells were also observed. Most callosal neurons corresponded to immature pyramidal cells. In addition, a few biocytin-labelled callosal neurons displayed extremely fusiform shapes, vertical orientation and a short, single process emerging from the apical side of the perikaryon. At the electron microscopic level, these cells had features identical to those described for migrating callosal neurons. Twenty-four hours after birth, these migrating neurons were almost exclusively observed in the upper, dense aspect of the cortical plate (presumptive layers II-III) and only very exceptionally in the infragranular layers. No retrogradely labelled cell resembling migrating neurons were noticed after injections on postnatal days 2 or 5. To study migrating callosal neurons at embryonic stages, crystals of the lipophilic dye were injected in the corpus callosum or the contralateral white matter in embryos aged 17, 18 and 19 days, corresponding to the initial development of the corpus callosum in mice. Whereas callosal migrating neurons were not detected at embryonic days 17 and 18, injections of the lipophilic dye on embryonic day 19 revealed the presence of labelled migrating neurons in the infragranular layers. To corroborate further that these cells are migrating neurons, [3H]thymidine was administered on embryonic days 16 and 17, and labelled mice were injected with biocytin on embryonic day 19 or the first postnatal day. Retrogradely labelled callosal neurons resembling migrating neurons were autoradiographically labelled. These results indicate that the specification of certain neuronal types and the emergence of their cell type-specific characteristics occur shortly after postmitotic neurons leave the ventricular zone, before being positioned within the cortical plate.

Glutamate-like immunoreactivity and fate of Cajal-Retzius cells in the murine cortex as identified with calretinin antibody

Cortical layers VI to II develop between two layers of older neurons, the marginal and subplate zones, which are believed to have unique roles in cortical development. While subplate cells have been found essential for the establishment of thalamocortical relationships, the function of the marginal zone and in particular of the neurons of Cajal-Retzius has not been elucidated. Here we show that an antibody against the calcium-binding protein calretinin labels the population of Cajal-Retzius cells throughout their life in the murine cerebral cortex. In prenatal and early postnatal stages, Cajal-Retzius cells were found evenly distributed throughout the murine cerebral cortex. Cajal-Retzius-like neurons were also found in the developing hippocampus and dentate gyrus, which indicates that they may have a general function in cortical development. From P8 onward Cajal-Retzius cells disappeared from the neocortex and hippocampus, at the same time as degenerating immunoreactive neurons were observed. Calretinin-positive Cajal-Retzius cells were glutamate immunoreactive and their presumed axon terminals formed asymmetric synapses. These observations indicate that Cajal-Retzius cells may provide a tonic excitatory input, essential for the maturation of cortical neurons. Furthermore, since neuronal migration has been shown to be dependent on glutamate receptors, we propose that Cajal-Retzius cells releasing glutamate may direct migrating neuroblasts toward the marginal lamina, therefore creating the "inside-out" sequence of cortical development.

Transient dendritic appendages on differentiating septohippocampal neurons are not the sites of synaptogenesis

The factors which determine the final shape and synaptic connections of a neuronal phenotype are largely unknown. In adult animals, a large number of projection neurons, e.g. cortical pyramidal neurons, bear spines which, in the case of pyramidal cells, are postsynaptic elements of mainly asymmetric synapses. In contrast, mature septohippocampal neurons do not bear spines. During maturation, however, septohippocampal projection neurons develop a variety of dendritic appendages. Because the appearance of these processes falls into the period of synaptogenesis, it has been hypothesized that these transient appendages may be the site of synaptogenesis. Here we have investigated whether these transient dendritic appendages are the site of initial synaptic contacts of septohippocampal neurons. Septohippocampal projection neurons in late embryonic and early postnatal rats were identified by retrograde tracing with the carbocyanine dye DiI or biocytin. Subsequently, selected cells were processed for electron microscopy. Serial thin sections through identified dendritic appendages did not reveal synaptic contacts with presynaptic boutons but immature to mature synapses were always found on dendritic shafts or somata. Often, synapses are located close to the appendages. These data indicate that the transient appendages are not the place where ingrowing afferent fibers make their synapses. The available information about transient dendritic appendages suggests, that they may be involved in short-term contacts with ingrowing axons, without being themselves the final site of the synaptic contact.

Frequency and clinical associations of anti-chromo antibodies in connective tissue disease

OBJECTIVES

To assess the frequency and clinical associations of anti-chromo antibodies in connective tissue disease and to study their relationship to anti-centromere autoreactivity.

METHODS

Anti-chromo and anti-centromere antibodies (ACA) were measured by immunoblotting in 50 patients with systemic sclerosis (SSc) and 58 connective tissue disease controls. Common epitopes on centromere and chromo antigens were sought using affinity-purified antibodies from immunoblots.

RESULTS

Anti-chromo antibodies were detected in three of 32 sera with ACA and no controls. The three patients with anti-chromo antibodies had limited cutaneous SSc, and two had erosive arthritis. No cross-reactivity between chromo or centromere-related proteins was demonstrated.

CONCLUSIONS

Anti-chromo antibodies form a rare autoantibody specificity that may identify an overlap group of patients with SSc and arthritis. Chromo and centromere antigens are associated but immunologically distinct autoimmune targets. Whether they localise to the same chromosomal site remains unknown.

The development of parvalbumin-immunoreactivity in the neocortex of the mouse

In the present study the postnatal development of parvalbumin-immunoreactivity was examined in the neocortex of the mouse. Postnatal mice were processed at different developmental stages using a well-characterized monoclonal antibody against parvalbumin, and immunocytochemistry. The first immunoreactive neurons appeared in the first parietal and retrosplenial cortices at postnatal day 10 (P10). From P11 to P12, immunoreactivity emerged in the second parietal, cingular, frontal, hindlimb-forelimb, first temporal, primary and secondary occipital and gustatory cortices, and at P14, parvalbumin-positive cells were present in the remaining regions. In general, parvalbumin-immunoreactivity appeared first in the primary sensory/motor areas, and then in second sensory/motor or associative areas. The maturation of parvalbumin-immunoreactivity, however, was a long-lasting process, which was not completed until adult stages. In all cortical regions, parvalbumin-immunoreactive cells were present first in layer V, from which immunoreactivity expanded to the upper and inner cortical layers at subsequent developmental stages. This pattern of maturation differed from the usual 'inside-out' gradient of neocortical neurogenesis and maturation. At the cellular level, parvalbumin-immunoreactivity appeared first in cell somata, and staining of dendrites and boutons was apparent two days later. From the second postnatal week onwards, an immunoreactive axonal system was observed in the neocortical white matter and the corpus callosum. We conclude that the emergence and maturation of parvalbumin-immunoreactivity in the mouse neocortex shows marked area-specific differences, but proceeds following a similar center-to-outside radial gradient. These features may reflect the acquisition of certain physiological properties by a subset of GABAergic inhibitory neurons.

Transcripts encoding a neural membrane CD26 peptidase-like protein are stimulated by synaptic activity

We isolated a cDNA clone, named BSPL, that encodes a brain-specific dipeptidyl peptidase-like protein with 30% identity and 50% similarity to CD26, a lymphocyte membrane antigen involved in T-cell activation. BSPL lacks, however, the catalytic residue responsible for peptidase activity. The expression of BSPL is widespread throughout the CNS but restricted to neurons under normal conditions. Twenty-four hours after injection of kainic acid into the hippocampus, a dramatic increase in the concentration of BSPL mRNA was detected by in situ hybridization in the CA3 region of the injected hemisphere as compared with the contralateral hemisphere or sham-injected animals. An increase in the steady-state level of BSPL mRNA concentration was also found following tetanic stimulation of the perforant path to produce LTP in granule cells of the dentate gyrus. Hybridization signals could be detected in dendritic processes of pyramidal neurons and in some glial cells upon either type of stimulation. These data suggest that BSPL may be involved in synaptic plasticity.

[138 episodes of bacteremia or fungemia in patients with solid organ (renal or hepatic) transplantation]

BACKGROUND

To study the bacteremias and fungemias of the patients with solid organ transplantation (kidney or liver) and analyze the differences according to the type of graft.

METHODS

A prospective study included in a control program of bacteremias of a 1000-bed hospital and a follow up study of the infections of the patients who had undergone kidney transplantation (KT) (1985-1991) and liver transplantation (LT) (1988-1991) were carried out.

RESULTS

One hundred thirty-one bacteremias and 5 fungemias, 75 in 62 patients with KT out of a total of 568 transplantations (11%) and 63 out of 54 patients with LT out of a total of 185 transplantations (29%) were identified. The prevalence of bacteremia in LT was greater (p < 0.001). The origin was nosocomial in 95% in LT and 70% in KT (p < 0.001). Around 50% of the bacteremias occurred during the first month post LT and KT. The microorganisms isolated were: Staphylococcus sp. (21 in KT and 30 in LT), with greater incidence in LT (p < 0.05); Enterococcus sp. (9 and 5, respectively), enterobacterias (12 and 12, respectively), Pseudomonas sp. (14 and 6, respectively), Candida sp. (2 and 3, respectively) with similar rates in both transplants. The origin of bacteremia was; renal and urinary tract, most frequent in KT (21 and 2 respectively) (p = 0.001). The origin of bacteremia was: renal and urinary tract, most frequent in KT (21 and 2 respectively) (p < 0.001), intraabdominal and biliary tract, most frequent in LT (4 and 14, respectively) (p = 0.007); intravenous catheter, most frequent in LT (16 and 24 respectively) (p < 0.05); lung, most frequent in LT although without statistical significance (3 and 8, respectively), (p = NS), and finally, surgical wound (4 and 1, respectively) (p = NS). Seventeen patients died (14 with LT and 3 with KT).

CONCLUSIONS

The incidence of bacteremia and the mortality related, was greater in LT than that observed in KT. The most frequent origin in KT was the kidney and urinary tract and the biliary and intraabdominal organs and the intravenous catheter were most prevalent in liver transplants. Staphylococcus sp was the most frequent germ in both types of transplantation and polymicrobian infection in liver transplants. Gram-negative germs caused higher mortality in liver transplantation.